Various coupling devices have been developed which connect a first conduit or pipe to a second conduit or pipe. Typically these couplings include a female receptacle secured to one end of the first conduit to be connected and a mating male plug secured to one end of the second conduit. The conduits are connected together by securing the male plug in position within the female receptacle in a fluid-tight manner.
Several methods of securing the male plug to the receptacle have been employed. In earlier couplings, the receptacle was provided with a threaded chamber sized to receive the plug. The plug was equipped with mating threads so that the plug and the receptacle could be screwed together to complete the connection. This has proven, however, to be an ineffective and time consuming method of connecting conduits.
More recently, "plug-in" type couplings have been developed whereby the male plug is slideably received and secured within the female receptacle chamber without screwing the mating parts together. This type of coupling has the advantage of providing a quick connect configuration since the plug is pushed into the receptacle without the time consuming turning motion.
"Plug-in" couplings typically employ a single, shaped spring positioned within an opening in the receptacle, which extends through the exterior of the receptacle into the inner chamber to secure the plug.
In one common configuration, the spring secures the plug by engaging a circumferential groove or recess in the outer surface of the plug to prevent axial displacement of the plug relative to the receptacle. Some examples of couplings employing this configuration include U.S. Pat. Nos. 3,625,551, 3,628,768, 4,278,296, 4,635,974 as well as German Pat. Pub. Nos. DE 2,028,711 and DE 3,440,753.
In another common configuration, the spring secures the plug by resting against a peripheral flange on the plug. U.S. Pat. Nos. 3,314,696, 4,768,587, 4,772,052 and British Pat. Pub. No. GB 1,030,535 are a few examples of these types of couplings.
Both of these configurations suffer from the numerous shortcomings, namely the opening in the receptacle exposes the inner portion of the coupling to the corrosive effects of the environment and the complex shaped springs are expensive to manufacture as well as difficult to install. Furthermore, the pinching or squeezing of the spring to detach the plug from the receptacle is awkward and often requires the use of a tool, such as a screwdriver.